A new series of pyrazole derivatives have been synthesized by the reaction of substituted pyrazole carbohydrazide
and functionalized aromatic aldehydes. All the compounds have been characterized by IR, 1H-NMR and mass
spectroscopy. The analgesic activity of the synthesized compound was assessed by tail flick method (for central
action) in rat, acetic acid-induced writhing test (for peripheral action) in mice. The effect of the synthesized
compounds N’-(2,4-dichlorobenzylidene)-5-methyl-1H-pyrazol-3-carbohydrazide (5a), N\'-(2,4-dichlorobenzylidene)-2-(3,5-dimethyl-1H-pyrazol-1-yl)acetohydrazide(9),
N’-(4-dimethylaminobenzyli-dene)-5-phenyl-1H-pyrazol
-3-carbohydrazide (5b) and N’-(2,4-dichlorobenzylidene) -5-phenyl-1H-pyrazol-3-carbohydrazide (5c) was also
investigated in a battery of behavioural models in mice to assess their sedative effect. Among them, 5b was found
more potent in comparison to 150 mg/kg of acetylsalicylic acid (ASA) with 44.83% of inhibition. In radiant heat
tail-flick test the synthesized compounds 5a, 9, 5b and 5c produced 11.06%, 9.73%, 8.38% and 19.31% (p<0.01)
elongation of tail flicking time 30 minutes after oral doses of 100 mg/Kg body weight respectively. Further
compounds after 60 min, the inhibition of pain were 8.27%, 8.97%, 6% and 12.98% respectively. The synthesized
compounds at doses of 50 mg/Kg body weight tested were insignificant when compared with the control.
Furthermore the oral administration in mice of compounds at 50 and 100 mg / kg, induces strong sedative effect
compared to reference substance Nesdonal and significantly reduced in both the reestablishment time and number
of head dips during the traction and hole-board tests, in the rotarod test the pyrazole derivatives significantly
reduced the motor coordination of the tested animals. From the results the pyrazole derivatives exhibited antinociceptive
activity by central and peripheral mechanism(s) and possess potent sedative effect.